David Clarke speaks at the Republican national convention in 2016, where he proclaimed “blue lives matter”.
Photograph: J Scott Applewhite/AP

The controversial Milwaukee County sheriff, David Clarke, who has compared Black Lives Matter to the Ku Klux Klan, has said he is joining the Trump administration as a point person between federal government and local and state law enforcement.

Clarke broke the news of his appointment on the local Wisconsin radio station 1130 WISN Radio. The move brings to an end a long courtship between Trump and the sheriff, who acted as a surrogate for the Republican nominee on the campaign trail last year and was one of few African American speakers at the Republican national convention, at which he proclaimed “blue lives matter” in homage to police officers.

Sheriff David Clarke Jr: the black Democrat who is Trump's favorite cop

Read more

The appointment of Clarke as assistant secretary of the Department of Homeland Security, and his consequent stepping down as sheriff in Wisconsin’s biggest city, will be greeted with delight by Milwaukee immigrant and minority groups who have accused him of encouraging racial profiling among his deputies. The move suggests that the Trump administration may continue to push local police jurisdictions to play a bigger role alongside federal immigration officials in rounding up undocumented immigrants – a policy that Clarke himself had begun to adopt in Milwaukee.

In an interview with the Guardian in March, the sheriff said he was in favor of local law enforcers acting as immigration agents in apprehending undocumented individuals who had committed even the most basic misdemeanours. “I don’t think it’s too much to ask for someone in this country illegally to abide by all our laws – I don’t care what the crime is. If I went to Mexico, I don’t get to engage in misdemeanor crimes and then say, ‘Well, it’s just a misdemeanor.”

He also dismissed accusations of racial profiling. “Let’s define what we profile: we profile criminal behavior, not ethnicity. This term ‘racial profiling’ is thrown out there as flame-throwing – call them racist! – I’m not afraid of that crap.”

Clarke’s critics have questioned his suitability for federal office, given the patchy track record of the sheriff’s department in Milwaukee County. One of his duties is overseeing the county jail, which in the past year has seen four deaths among its inmates.

One of those to die was a 38-year-old man with bipolar disorder who was found to have suffered dehydration after his water supply was cut off for six days in response to his erratic behavior. The death was ruled a homicide.

Clarke said that all four deaths were routine, but when asked by the Guardian how he explained a death by dehydration under his care, he replied: “This guy was in bad health. It was a contributing factor.”

Reacting to his announcement on Wednesday, the immigrant advocacy group Voces de la Frontera said he was “unfit for office” and should face charges over the deaths in jail. The group, which also called on Governor Scott Walker to end collaboration with Trump’s immigration crackdown, said: “Trump’s appointment of Clarke shows this administration’s disregard for human rights.”

The sheriff is known for his colourful and provocative use of language, and has been dubbed the “black Rush Limbaugh with a badge”. He frequently makes pugilistic remarks on social media and at rallies, including calling a Milwaukee resident a “snowflake” after a contretemps onboard a plane.

At Trump’s inauguration celebrations in January, he told a crowd that the only time he would reach across the aisle to work with liberals would be to “grab one of them by the throat”.

“I play smash-mouth politics,” he told the Guardian. “Politics is a contact sport. I didn’t create the rules. It’s hit or be hit. I understand the environment. People are trying to slit my throat politically and personally, so you better be ready when they come after you.”

At a time when Trump has been advised by senior Republicans to impose greater message discipline on the White House, Clarke’s promotion to the national stage is unlikely to introduce a calmer tone to political debate. He is a fierce partisan, even though he stands for election in Milwaukee as a Democrat – a necessary compromise for one seeking office in that historically Democratic city.

In a recent tweet, he lashed out at media coverage of Trump’s recent travails, using forthright language that surpassed even the president’s own. “The swamp creatures in the Beltway have mounted yet another all out assault on @realDonaldTrump. He beat em back before & he’ll do it again,” he wrote.